1. Field of the Invention
This invention relates to a microscope and, in articular, to a zoom capability, specimen heating capability and objective lens positioning capability of a microscope. The invention further relates to the use of a microscope for liquid crystal analysis of a semiconductor device and, in particular, to a microscope for such use that is portable.
2. Related Art
Microscopic liquid crystal analysis is sometimes used to perform failure analysis of semiconductor devices. Previously, microscopic liquid crystal analysis of semiconductor devices has been performed using large, bulky, heavy microscopes. For example, large probe station microscopes (such as made by SUSS MicroTec, located in Waterbury, Vt. and headquartered in Munich, Germany, or by Signatone Corporation located in Gilroy, Calif.) that have been used for microscopic liquid crystal analysis of semiconductor devices have weighed between 500 and 1500 pounds. The microscopes previously used for microscopic liquid crystal analysis of semiconductor devices cannot be moved easily or at all. For example, it is typically not feasible to transport a liquid crystal analysis microscope to a location that is geographically remote from that at which the microscope is usually located (because, for example, such microscopes are too large and heavy to be transported as luggage on a commercial airliner), making a field visit to a distant location impractical. Even when it is possible to move a liquid crystal analysis microscope, special equipment and/or packaging is required to transport the microscope, making transportation of the microscope unduly expensive and time consuming. Consequently, the performance of microscopic liquid crystal analysis of a semiconductor device has necessitated that the semiconductor device be transported to the location of the microscope to be used to perform the analysis. This can be disadvantageous. For example, this can preclude analysis of a semiconductor device together with a system of which the semiconductor device is part. Analyzing a semiconductor device apart from a system of which the semiconductor device is part may result in an inability to reproduce a problem that instigated the analysis of the semiconductor device and/or may inhibit the ability to test solutions to problems with operation of the semiconductor device. Additionally, transporting a semiconductor device to the location of an analysis microscope may be inconvenient, impractical, unduly time consuming and/or impossible.
It is sometimes desirable for a microscope to have a zoom capability (i.e., the capability of continuously changing the microscope magnification over a range of magnifications). The structure used in previous microscopes to provide zoom capability can be undesirable in some respects. For example, zoom capability is provided in some microscopes by a zoom lens that is positioned in a microscope body in the optical path of the microscope (e.g., between the eyepiece and a fixed objective lens) and coupled to a system of gears and knobs that enable the zoom lens to be moved with respect to the microscope body, thereby enabling continuous change in the microscope magnification. Such structure can be undesirably expensive. Such structure may also not enable as wide a range of magnifications as desired (e.g., a highest magnification that is two or more times the lowest magnification). Further, the structure previously used for providing zoom capability in microscopes has been undesirably heavy. For example, to maintain a stable optical path, the zoom apparatus of previous microscopes can include a heavy (e.g., about 3 pounds) steel tube which housed mechanical gear apparatus and a knob. Additionally, for microscopes including multiple objective lenses, providing zoom capability for the entire range of magnification of the microscope requires that each of the objective lenses be optically matched to the zoom apparatus, which can increase the complexity and cost of constructing the microscope. Moreover, microscopes including multiple objective lenses have not provided continuous zoom capability over the entire magnification range of the objective lenses.
During operation of a microscope, it is sometimes necessary to adjust the relative positions of a specimen and the objective lens being used to observe the specimen in order to facilitate, enable or improve observation of the specimen. This has been accomplished by providing a movable stage on which the specimen is mounted, thereby enabling the specimen to be moved as necessary to achieve an appropriate relative position of the specimen and objective lens. Since the specimen must be mounted on the microscope stage, the specimen cannot be observed while positioned in the environment in which the specimen normally exists. This can be disadvantageous in some applications. For example, in performing microscopic liquid crystal analysis of a semiconductor device, it can be desirable (for both problem diagnosis and solution) to observe the semiconductor device as the semiconductor device operates in an electronic system of which the semiconductor device is part. However, this is infeasible or impossible when the semiconductor device must be mounted on a microscope stage.
It can be desirable in some situations to control the temperature of a specimen during analysis of the specimen with a microscope. For example, the sensitivity of microscopic liquid crystal analysis of a semiconductor device can be increased by heating the semiconductor device. Previously, such heating has been accomplished using a radiant heating wire located under the semiconductor device (i.e., on the side of the semiconductor device opposite that being observed with the microscope).